(Alt: The Drake meme. Upper panel shows him hiding his face from "Securing Customer Data". Lower panel shows him smirking at "Securing Public API Documentation")
Any company that hides their documentation has an awful product that they are actually embarrassed about, from a tech perspective. They are hiding it because they are afraid to show it.
I've seen this so many times, and it's a big red flag.
These companies work on the basis of selling their product the old-fashioned way, directly to management with sales-people and business presentations and firm handshakes, and then once you're sold then developers (which management doesn't care about by the way) have to do the odious task of getting everything working against their terrible and illogical API. And when you need help implementing, then your single point of contact is one grumpy-ass old dev working in a basement somewhere (because they don't care about their own devs either) and he's terribly overstretched due to the number of other customers he's also trying to help, because their implementation is so shitty.
Conversely, public documentation is a great sign that companies took a developer-led approach to designing their solution, that it will be easy to implement, that they respect the devs within their own company, and they will also respect yours.
When I am asked to evaluate potential solutions for a problem, Public docs is like the number one thing I care about! It's just that significant.
Side story - I once worked with one of these shitty vendors, and learned from a tech guy I'd made friends with that the whole company was basically out of office on a company-paid beach holiday - EXCEPT for the dev team. Management, sales, marketing, finance, they all got a company trip, but the tech peeps had to stay at home. Tells you everything you need to know about their management attitude towards tech.
